source3/smbd/smb2_signing.c

   1 /*
   2    Unix SMB/CIFS implementation.
   3    SMB2 signing
   4
   5    Copyright (C) Stefan Metzmacher 2009
   6
   7    This program is free software; you can redistribute it and/or modify
   8    it under the terms of the GNU General Public License as published by
   9    the Free Software Foundation; either version 3 of the License, or
  10    (at your option) any later version.
  11
  12    This program is distributed in the hope that it will be useful,
  13    but WITHOUT ANY WARRANTY; without even the implied warranty of
  14    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
  15    GNU General Public License for more details.
  16
  17    You should have received a copy of the GNU General Public License
  18    along with this program.  If not, see <http://www.gnu.org/licenses/>.
  19 */
  20
  21 #include "includes.h"
  22 #include "smbd/globals.h"
  23 #include "../libcli/smb/smb_common.h"
  24 #include "../lib/crypto/crypto.h"
  25
  26 NTSTATUS smb2_signing_sign_pdu(DATA_BLOB session_key,
  27                                struct iovec *vector,
  28                                int count)
  29 {
  30         uint8_t *hdr;
  31         uint64_t session_id;
  32         struct HMACSHA256Context m;
  33         uint8_t res[SHA256_DIGEST_LENGTH];
  34         int i;
  35
  36         if (count < 2) {
  37                 return NT_STATUS_INVALID_PARAMETER;
  38         }
  39
  40         if (vector[0].iov_len != SMB2_HDR_BODY) {
  41                 return NT_STATUS_INVALID_PARAMETER;
  42         }
  43
  44         hdr = (uint8_t *)vector[0].iov_base;
  45
  46         session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
  47         if (session_id == 0) {
  48                 /*
  49                  * do not sign messages with a zero session_id.
  50                  * See MS-SMB2 3.2.4.1.1
  51                  */
  52                 return NT_STATUS_OK;
  53         }
  54
  55         if (session_key.length == 0) {
  56                 DEBUG(2,("Wrong session key length %u for SMB2 signing\n",
  57                          (unsigned)session_key.length));
  58                 return NT_STATUS_ACCESS_DENIED;
  59         }
  60
  61         memset(hdr + SMB2_HDR_SIGNATURE, 0, 16);
  62
  63         SIVAL(hdr, SMB2_HDR_FLAGS, IVAL(hdr, SMB2_HDR_FLAGS) | SMB2_HDR_FLAG_SIGNED);
  64
  65         ZERO_STRUCT(m);
  66         hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m);
  67         for (i=0; i < count; i++) {
  68                 hmac_sha256_update((const uint8_t *)vector[i].iov_base,
  69                                    vector[i].iov_len, &m);
  70         }
  71         hmac_sha256_final(res, &m);
  72         DEBUG(5,("signed SMB2 message\n"));
  73
  74         memcpy(hdr + SMB2_HDR_SIGNATURE, res, 16);
  75
  76         return NT_STATUS_OK;
  77 }
  78
  79 NTSTATUS smb2_signing_check_pdu(DATA_BLOB session_key,
  80                                 const struct iovec *vector,
  81                                 int count)
  82 {
  83         const uint8_t *hdr;
  84         const uint8_t *sig;
  85         uint64_t session_id;
  86         struct HMACSHA256Context m;
  87         uint8_t res[SHA256_DIGEST_LENGTH];
  88         static const uint8_t zero_sig[16] = { 0, };
  89         int i;
  90
  91         if (count < 2) {
  92                 return NT_STATUS_INVALID_PARAMETER;
  93         }
  94
  95         if (vector[0].iov_len != SMB2_HDR_BODY) {
  96                 return NT_STATUS_INVALID_PARAMETER;
  97         }
  98
  99         hdr = (const uint8_t *)vector[0].iov_base;
 100
 101         session_id = BVAL(hdr, SMB2_HDR_SESSION_ID);
 102         if (session_id == 0) {
 103                 /*
 104                  * do not sign messages with a zero session_id.
 105                  * See MS-SMB2 3.2.4.1.1
 106                  */
 107                 return NT_STATUS_OK;
 108         }
 109
 110         if (session_key.length == 0) {
 111                 /* we don't have the session key yet */
 112                 return NT_STATUS_OK;
 113         }
 114
 115         sig = hdr+SMB2_HDR_SIGNATURE;
 116
 117         ZERO_STRUCT(m);
 118         hmac_sha256_init(session_key.data, MIN(session_key.length, 16), &m);
 119         hmac_sha256_update(hdr, SMB2_HDR_SIGNATURE, &m);
 120         hmac_sha256_update(zero_sig, 16, &m);
 121         for (i=1; i < count; i++) {
 122                 hmac_sha256_update((const uint8_t *)vector[i].iov_base,
 123                                    vector[i].iov_len, &m);
 124         }
 125         hmac_sha256_final(res, &m);
 126
 127         if (memcmp(res, sig, 16) != 0) {
 128                 DEBUG(0,("Bad SMB2 signature for message\n"));
 129                 dump_data(0, sig, 16);
 130                 dump_data(0, res, 16);
 131                 return NT_STATUS_ACCESS_DENIED;
 132         }
 133
 134         return NT_STATUS_OK;
 135 }